Ensure Cluster Machine Approver metrics are only available via HTTPS

Background

CMA currently exposes metrics on two ports via the 0.0.0.0 all hosts binding. We need to make sure that only the TLS port is accessible from outside localhost.

Steps

• Move the binding for the local metrics server to localhost only
• Ensure kube-rbac-proxy is still proxying the requests over TLS

Stakeholders

• Cluster Infra
• Subin M

Definition of Done

• Metrics from CMA are only exposed over TLS

• Docs

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• Testing

• <Explain testing that will be added>